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Antimicrobial Agents and Chemotherapy Jun 2024The emergence of clinically drug-resistant malaria parasites requires the urgent development of new drugs. Mosquitoes are vectors of multiple pathogens and have...
The emergence of clinically drug-resistant malaria parasites requires the urgent development of new drugs. Mosquitoes are vectors of multiple pathogens and have developed resistance mechanisms against them, which often involve antimicrobial peptides (AMPs). An-cecB is an AMP of the malaria-transmitting mosquito genus , and we herein report its antimalarial activity against 3D7, the artemisinin-resistant strain 803, and the chloroquine-resistant strain Dd2 . We also demonstrate its anti-parasite activity , using the rodent malaria parasite (ANKA). We show that An-cecB displays potent antimalarial activity and that its mechanism of action may occur through direct killing of the parasite or through interaction with infected red blood cell membranes. Unfortunately, An-cecB was found to be cytotoxic to mammalian cells and had poor antimalarial activity . However, its truncated peptide An-cecB-1 retained most of its antimalarial activity and avoided its cytotoxicity . An-cecB-1 also showed better antimalarial activity . Mosquito-derived AMPs may provide new ideas for the development of antimalarial drugs against drug-resistant parasites, and An-cecB has potential use as a template for antimalarial peptides.
PubMed: 38874346
DOI: 10.1128/aac.00311-24 -
Cureus May 2024Background In parallel with the eradication of indigenous malaria since 2005 and the certification of Morocco as a malaria-free country by the World Health Organization...
Background In parallel with the eradication of indigenous malaria since 2005 and the certification of Morocco as a malaria-free country by the World Health Organization in 2010, imported malaria cases are still being notified in Morocco. This study aims to describe the epidemiological profile and characterize the demographic, clinical, and biological profile of imported malaria cases diagnosed at the Central Laboratory of Parasitology-Mycology of the Ibn Sina University Hospital in Rabat, Morocco. Methodology This retrospective study analyzed 81 cases of imported malaria at Ibn Sina University Hospital's Central Laboratory of Parasitology-Mycology in Rabat, Morocco from January 2015 to December 2023. Patients meeting the inclusion criteria had contracted malaria in endemic regions, confirmed through parasitological evidence on blood smears. Results Among the 81 positive cases, 55 (63%) were male, resulting in a male-to-female ratio of approximately 3:1. The imported cases came from 15 countries in sub-Saharan Africa, mainly from Ivory Coast (31 patients, 31%) and Guinea (16 patients, 16%). The main clinical sign was fever (79 patients, 97.53%). The majority of patients (70 patients, 86%) suffered from anemia, while thrombocytopenia was present in 76% of patients (62 patients). was the most common species found in 77 (95%) cases and in two (2.5%) cases. However, was isolated in only one (1.23%) case. Only one case of co-infection by and (1.23%) was found. Parasitemia values due to were between 0.1% and 30%. On the other hand, those of other species did not exceed 2%. Conclusions In summary, among 81 imported malaria cases, 55 (63%) were men, imported mainly from 15 sub-Saharan African countries. was the predominant species. Fever was the most common clinical sign, accompanied by high rates of anemia and thrombocytopenia.
PubMed: 38872642
DOI: 10.7759/cureus.60253 -
Scientific Reports Jun 2024Among the factors affecting the effectiveness of malaria control is poor knowledge of the entomologic drivers of the disease. We investigated anopheline populations as...
Among the factors affecting the effectiveness of malaria control is poor knowledge of the entomologic drivers of the disease. We investigated anopheline populations as part of a baseline study to implement house screening of windows and doors as a supplementary malaria control tool towards elimination in Jabi Tehnan district, Amhara Regional State of Ethiopia. The samples were surveyed monthly using CDC light traps between June 2020 and May 2021. Mosquito trap density (< 3 mosquitoes/trap) was low, however, with a high overall Plasmodium sporozoite rate (9%; indoor = 4.3%, outdoor = 13.1%) comprising P. falciparum (88.9%) and P. vivax (11.1%). Anopheles gambiae s.l., mostly An. arabiensis, comprised > 80% of total anopheline captures and contributed ~ 42% of Plasmodium-infected mosquitoes. On the other hand, morphologically scored Anopheles funestus s.l., constituting about 6% of anopheline collections, accounted for 50% of sporozoite-infected mosquitoes. Most of the infected An. funestus s.l. specimens (86.7%) were grouped with previously unknown or undescribed Anopheles species previously implicated as a cryptic malaria vector in the western Kenyan highlands, confirming its wider geographic distribution in eastern Africa. Other species with Plasmodium infection included An. longipalpis C, An. theileri, An. demillioni, and An. nili. Cumulatively, 77.8% of the infected mosquitoes occurred outdoors. These results suggest efficient malaria parasite transmission despite the low vector densities, which has implications for effective endpoint indicators to monitor malaria control progress. Additionally, the largely outdoor infection and discovery of previously unknown and cryptic vectors suggest an increased risk of residual malaria transmission and, thus, a constraint on effective malaria prevention and control.
Topics: Ethiopia; Animals; Anopheles; Mosquito Vectors; Humans; Malaria; Plasmodium falciparum; Plasmodium vivax; Sporozoites; Mosquito Control; Malaria, Vivax; Malaria, Falciparum; Female
PubMed: 38871839
DOI: 10.1038/s41598-024-64436-3 -
PLoS Pathogens Jun 2024Plasmodium parasites, the causal agents of malaria, are eukaryotic organisms that obligately undergo sexual recombination within mosquitoes. In low transmission...
Plasmodium parasites, the causal agents of malaria, are eukaryotic organisms that obligately undergo sexual recombination within mosquitoes. In low transmission settings, parasites recombine with themselves, and the clonal lineage is propagated rather than broken up by outcrossing. We investigated whether stochastic/neutral factors drive the persistence and abundance of Plasmodium falciparum clonal lineages in Guyana, a country with relatively low malaria transmission, but the only setting in the Americas in which an important artemisinin resistance mutation (pfk13 C580Y) has been observed. We performed whole genome sequencing on 1,727 Plasmodium falciparum samples collected from infected patients across a five-year period (2016-2021). We characterized the relatedness between each pair of monoclonal infections (n = 1,409) through estimation of identity-by-descent (IBD) and also typed each sample for known or candidate drug resistance mutations. A total of 160 multi-isolate clones (mean IBD ≥ 0.90) were circulating in Guyana during the study period, comprising 13 highly related clusters (mean IBD ≥ 0.40). In the five-year study period, we observed a decrease in frequency of a mutation associated with artemisinin partner drug (piperaquine) resistance (pfcrt C350R) and limited co-occurence of pfcrt C350R with duplications of plasmepsin 2/3, an epistatic interaction associated with piperaquine resistance. We additionally observed 61 nonsynonymous substitutions that increased markedly in frequency over the study period as well as a novel pfk13 mutation (G718S). However, P. falciparum clonal dynamics in Guyana appear to be largely driven by stochastic factors, in contrast to other geographic regions, given that clones carrying drug resistance polymorphisms do not demonstrate enhanced persistence or higher abundance than clones carrying polymorphisms of comparable frequency that are unrelated to resistance. The use of multiple artemisinin combination therapies in Guyana may have contributed to the disappearance of the pfk13 C580Y mutation.
Topics: Plasmodium falciparum; Guyana; Malaria, Falciparum; Humans; Antimalarials; Drug Resistance; Artemisinins; Mutation; Protozoan Proteins
PubMed: 38870266
DOI: 10.1371/journal.ppat.1012013 -
Microbiology Spectrum Jun 2024Malaria infection remains a serious threat to human health worldwide. Rapid and accurate detection technology is crucial for preventing malaria transmission and...
UNLABELLED
Malaria infection remains a serious threat to human health worldwide. Rapid and accurate detection technology is crucial for preventing malaria transmission and minimizing damage. We aimed to establish and validate a new rapid molecular detection method for malaria, called EasyNAT Malaria Assay, targeting , , , and . The analytical performance of EasyNAT Malaria Assay was determined using positive materials. We identified 42 clinical samples as malaria positive and 95 negative samples. Each sample was examined by four methods: light microscopy, rapid diagnostic test, EasyNAT Malaria Assay, and digital PCR. Diagnostic accuracy and clinical performance were evaluated. The limit of detection (LOD) of EasyNAT Malaria was consistently 40 parasites/mL. It specifically amplified and performed with reliable repeatability and reproducibility. In 137 clinical samples, EasyNAT Malaria detected four more positive samples than microscopic examination and two more positive samples than rapid diagnostic test (RDT). One clinical sample was positive only under digital PCR. However, no significant differences statistically in sensitivity or specificity were observed. Compared with microscopy, the total, positive, and negative concordance rates of EasyNAT were 97.08%, 100%, and 95.79%, respectively. Enhanced diagnostic accuracy of EasyNAT Malaria in patients who had taken anti-malarial medication before their clinical appointment was observed. The EasyNAT Malaria Assay has good detection efficiency for clinical samples, presents a promising molecular detection tool in clinical practice, and is particularly suitable for rapid screening of high-risk populations in the emergency room.
IMPORTANCE
This study established and validated EasyNAT Malaria Assay as a promising molecular detection tool for malaria screening of high-risk populations in clinical practice. This novel isothermal amplification method may effectively facilitate the rapid diagnosis of malaria and prevent its transmission.
PubMed: 38869308
DOI: 10.1128/spectrum.00583-24 -
Cureus May 2024Introduction Malaria is a major public health concern, especially in developing countries. Malaria often presents with recurrent fever, malaise, and other nonspecific...
Introduction Malaria is a major public health concern, especially in developing countries. Malaria often presents with recurrent fever, malaise, and other nonspecific symptoms mistaken for influenza. Light microscopy of peripheral blood smears is considered the gold standard diagnostic test for malaria. Delays in malaria diagnosis can increase morbidity and mortality. Microscopy can be time-consuming and limited by skilled labor, infrastructure, and interobserver variability. Artificial intelligence (AI)-based tools for diagnostic screening can automate blood smear analysis without relying on a trained technician. Convolutional neural networks (CNN), deep learning neural networks that can identify visual patterns, are being explored for use in abnormality detection in medical images. A parameter that can be optimized in CNN models is the batch size or the number of images used during model training at once in one forward and backward pass. The choice of batch size in developing CNN-based malaria screening tools can affect model accuracy, training speed, and, ultimately, clinical usability. This study explores the impact of batch size on CNN model accuracy for malaria detection from thin blood smear images. Methods We used the publicly available "NIH-NLM-ThinBloodSmearsPf" dataset from the United States National Library of Medicine, consisting of blood smear images for Plasmodium falciparum. The collection consists of 13,779 "parasitized" and 13,779 "uninfected" single-cell images. We created four datasets containing all images, each with unique randomized subsets of images for model testing. Using Python, four identical 10-layer CNN models were developed and trained with varying batch sizes for 10 epochs against all datasets, resulting in 16 sets of outputs. Model prediction accuracy, training time, and F1-score, an accuracy metric used to quantify model performance, were collected. Results All models produced F1-scores of 94%-96%, with 10 of 16 instances producing F1-scores of 95%. After averaging all four dataset outputs by batch size, we observed that, as batch size increased from 16 to 128, the average combined false positives plus false negatives increased by 15.4% (130-150), and the average model F1-score accuracy decreased by 1% (95.3%-94.3%). The average training time also decreased by 28.11% (1,556-1,119 seconds). Conclusion In each dataset, we observe an approximately 1% decrease in F1-score as the batch size was increased. Clinically, a 1% deviation at the population level can create a relatively significant impact on outcomes. Results from this study suggest that smaller batch sizes could improve accuracy in models with similar layer complexity and datasets, potentially resulting in better clinical outcomes. Reduced memory requirement for training also means that model training can be achieved with more economical hardware. Our findings suggest that smaller batch sizes could be evaluated for improvements in accuracy to help develop an AI model that could screen thin blood smears for malaria.
PubMed: 38868293
DOI: 10.7759/cureus.60224 -
RSC Advances Jun 2024To combat resistance against current antimalarials, modifying key pharmacophores and exploring novel parasite-specific drug targets remained one of the key drug design...
To combat resistance against current antimalarials, modifying key pharmacophores and exploring novel parasite-specific drug targets remained one of the key drug design strategies. The resistance to quinoline-based antimalarials arises often due to the efflux of the drug. Hence, the development of newer agents containing bulkier pharmacophores will enable medicinal chemists to counteract drug resistance. In view of this, herein we designed bulkier quinoline-furanone hybrids. Initially, virtual drug-likeness and ADMET screening were conducted to optimize physicochemical properties followed by docking of the hybrids against the lactate dehydrogenase (LDH) enzyme. The most potent hybrids that emerged from the computational screening were synthesized and screened for their bioactivity against the resistant strain of through Schizont Maturation Inhibition assays. Among the compounds tested, 5g and 6e demonstrated the best activity, with IC values similar to chloroquine (CQ), and 5g exhibited superior LDH inhibition compared to CQ. Compounds 5f, 7a, and 7f showed IC values comparable to CQ and moderate LDH inhibition. Structure-activity relationship (SAR) analysis revealed that halogen substitutions, particularly Br and Cl, enhanced antimalarial activity, while strong electron-withdrawing (-NO) or -donating (-OH) groups led to diminished activity. Additionally, bulkier aromatic substitutions were favoured for antimalarial activity and LDH inhibition. The investigation successfully found potent anti-plasmodial quinoline-furanone hybrids, demonstrating promising prospects for combating malaria.
PubMed: 38867738
DOI: 10.1039/d4ra01804d -
Malaria Journal Jun 2024Malaria remains a major global health problem although there was a remarkable achievement between 2000 and 2015. Malaria drug resistance, along with several other...
BACKGROUND
Malaria remains a major global health problem although there was a remarkable achievement between 2000 and 2015. Malaria drug resistance, along with several other factors, presents a significant challenge to malaria control and elimination efforts. Numerous countries in sub-Saharan Africa have documented the presence of confirmed or potential markers of partial resistance against artemisinin, the drug of choice for the treatment of uncomplicated Plasmodium falciparum malaria. The World Health Organization (WHO) recommends regular surveillance of artemisinin therapeutic efficacy to inform policy decisions.
METHODS
This study aimed to evaluate the therapeutic efficacy of artemether-lumefantrine (AL), which is the first-line treatment for uncomplicated P. falciparum malaria in Ethiopia since 2004. Using a single-arm prospective evaluation design, the study assessed the clinical and parasitological responses of patients with uncomplicated P. falciparum malaria in Metehara Health Centre, central-east Ethiopia. Out of 2332 malaria suspects (1187 males, 1145 females) screened, 80 (50 males, 30 females) were enrolled, followed up for 28 days, and 73 (44 males, 29 females) completed the follow up. The study was conducted and data was analysed by employing the per-protocol and Kaplan-Meier analyses following the WHO Malaria Therapeutic Efficacy Evaluation Guidelines 2009.
RESULTS
The results indicated rapid parasite clearance and resolution of clinical symptoms, with all patients achieving complete recovery from asexual parasitaemia and fever by day (D) 3. The prevalence of gametocytes decreased from 6.3% on D0 to 2.5% on D2, D3, D7, and ultimately achieving complete clearance afterward.
CONCLUSION
The overall cure rate for AL treatment was 100%, demonstrating its high efficacy in effectively eliminating malaria parasites in patients. No serious adverse events related to AL treatment were reported during the study, suggesting its safety and tolerability among the participants. These findings confirm that AL remains a highly efficacious treatment for uncomplicated P. falciparum malaria in the study site after 20 years of its introduction in Ethiopia.
Topics: Humans; Ethiopia; Malaria, Falciparum; Artemether, Lumefantrine Drug Combination; Male; Female; Antimalarials; Adult; Adolescent; Young Adult; Child, Preschool; Child; Prospective Studies; Middle Aged; Infant; Artemisinins; Fluorenes; Treatment Outcome; Ethanolamines; Aged; Drug Combinations; Plasmodium falciparum
PubMed: 38867217
DOI: 10.1186/s12936-024-04991-2 -
Microbiology Spectrum Jun 2024A hallmark of cerebral malaria (CM) is sequestration of -infected erythrocytes (IE) within the brain microvasculature. Binding of IE to endothelium reduces microvascular...
UNLABELLED
A hallmark of cerebral malaria (CM) is sequestration of -infected erythrocytes (IE) within the brain microvasculature. Binding of IE to endothelium reduces microvascular flow and, combined with an inflammatory response, perturbs endothelial barrier function, resulting in breakdown of the blood-brain barrier (BBB). Cytoadherence leads to activation of the endothelium and alters a range of cell processes affecting signaling pathways, receptor expression, coagulation, and disruption of BBB integrity. Here, we investigated whether CM-derived parasites elicit differential effects on human brain microvascular endothelial cells (HBMECs), as compared to uncomplicated malaria (UM)-derived parasites. Patient-derived IE from UM and CM clinical cases, as well as non-binding skeleton-binding protein 1 knockout parasites, were overlaid onto tumour necrosis factor (TNF)-activated HBMECs. Gene expression analysis of endothelial responses was performed using probe-based assays of a panel of genes involved in inflammation, apoptosis, endothelial barrier function, and prostacyclin synthesis pathway. We observed a significant effect on endothelial transcriptional responses in the presence of IE, yet there was no significant correlation between HBMEC responses and type of clinical syndrome (UM or CM). Furthermore, there was no correlation between HBMEC gene expression and both binding itself and level of IE binding to HBMECs, as we detected the same change in endothelial responses when employing both binding and non-binding parasites. Our results suggest that interaction of IE with endothelial cells in this co-culture model induces some endothelial responses that are independent of clinical origin and independent of the expression of the major variant antigen erythrocyte membrane protein 1 on the IE surface.
IMPORTANCE
Cerebral malaria (CM) is the most prevalent and deadly complication of severe infection. A hallmark of this disease is sequestration of -infected erythrocytes (IE) in brain microvasculature that ultimately results in breakdown of the blood-brain barrier. Here, we compared the effect of parasites derived from uncomplicated malaria (UM) and CM cases on the relative gene expression of human brain microvascular endothelial cells (HBMECs) for a panel of genes. We observed a significant effect on the endothelial transcriptional response in the presence of IE, yet there is no significant correlation between HBMEC responses and the type of clinical syndrome (UM or CM). Furthermore, there was no correlation between HBMEC gene expression and both binding itself and the level of IE binding to HBMECs. Our results suggest that interaction of IE with endothelial cells induces endothelial responses that are independent of clinical origin and not entirely driven by surface erythrocyte membrane protein 1 expression.
PubMed: 38864616
DOI: 10.1128/spectrum.00727-24 -
Frontiers in Immunology 2024Despite decades of effort, malaria remains a leading killer of children. The absence of a highly effective vaccine and the emergence of parasites resistant to both...
BACKGROUND
Despite decades of effort, malaria remains a leading killer of children. The absence of a highly effective vaccine and the emergence of parasites resistant to both diagnosis as well as treatment hamper effective public health interventions.
METHODS AND RESULTS
To discover new vaccine candidates, we used our whole proteome differential screening method and identified PfGBP130 as a parasite protein uniquely recognized by antibodies from children who had developed resistance to infection but not from those who remained susceptible. We formulated PfGBP130 as lipid encapsulated mRNA, DNA plasmid, and recombinant protein-based immunogens and evaluated the efficacy of murine polyclonal anti-PfGBP130 antisera to inhibit parasite growth in vitro. Immunization of mice with PfGBP130-A (aa 111-374), the region identified in our differential screen, formulated as a DNA plasmid or lipid encapsulated mRNA, but not as a recombinant protein, induced antibodies that inhibited RBC invasion . mRNA encoding the full ectodomain of PfGBP130 (aa 89-824) also generated parasite growth-inhibitory antibodies.
CONCLUSION
We are currently advancing PfGBP130-A formulated as a lipid-encapsulated mRNA for efficacy evaluation in non-human primates.
Topics: Animals; Plasmodium falciparum; Antibodies, Protozoan; Mice; Erythrocytes; Malaria, Falciparum; Humans; Malaria Vaccines; Protozoan Proteins; Antigens, Protozoan; Immunization; Female
PubMed: 38863702
DOI: 10.3389/fimmu.2024.1350560